Fitness devices, such as dumbbells, kettlebells, medicine balls, and sandbags, are common parts of gyms, and many people use them in their homes. Dumbbells, bar bells, and kettlebells tend to be heavy chunks of metal with a handle or bar and come in sets of fixed weights to meet the needs of a diverse public using them and for a diverse set of exercises targeting specific muscle groups. These devices in this form have been used for many years and are still used today. A more recent addition has been softer weights, such as sandbags and medicine balls, that offer a different array of potential exercises.